If anything, the fact we’re not seeing random drones carrying explosives and diving into groups of people on a daily basis shows the vast, vast (99.999%) majority of people is actually well-meaning and has no desire to kill or hurt anyone.
If you’re legitimately baffled by a random guy being able to fly a quadcopter around without any kind of government approval or oversight, I encourage you to buy one and play around (without explosives please!), just make sure to not fly it over places where people could be standing - terminal velocity is real and even a light one could cause serious injury if it were to lose control and fall on someone’s head.
Here in the USA quad-copter drones are used to inspect powerlines and other infrastructure; I see them a few times per year in my area. I don’t see why they wouldn’t use drones to visually inspect train tracks as well. Very cost effective and energy efficient alternative to manual inspection in a vehicle of some kind.